9th ECCC European Continuous Casting Conference – ECCC 2017

Optimization of CaO-SiO2-CaF2 based flux in a continuous steel caster should be determined from the view point of dual viscous functions for minimizing slab surface defects - high viscosity enough to alleviate flux entrainment at mold top surface where shear rate is about 10 – 40 reciprocal second and low viscosity enough to maximize lubrication capability at oscillated mold wall region where shear rate is around 100 – 1000 reciprocal second. Appropriate liquid mold flux with a strong shear thinning behavior showing significant decreasing tendency of viscosity with increasing shear rates has to be developed for sound slab quality. Flux viscosity was measured by a rotational type viscometer as a function of shear rates. Raman and XPS analysis were employed to understand structural changes of flux for correlating with shear thinning behavior. The present work has focused on developing an optimum mold flux system with strong shear thinning behavior. The strong shear thinning behavior appropriate for dual viscous functions could be achieved by incorporating silicon nitride or silicon carbide into network structure of the liquid flux. The flux compositions with a strong shear thinning behavior will be presented from the viewpoint of clean slab production.